Spin Cycle-Out of Control Vibration

The spin cycle starts out properly, however as it gains speed it starts a violent shake like it it totaly out of balance. It does this with no clothes in the tub,

I thought our washer was out of balance once, was walking on floor ,vibrating. but ended up being one of the shock absorber had come loose. just hooked it back up and spin cycle was good again. may want to check. Craig

Pull the outer panel out and check the skate board under the tub particularly if it was moved recently, if ok, check if one of the 3 springs has come off the frame.

As you suggested I took the pump off and turned the grear clockwise and it turned OK. I then notieced that one of the pad on the base assembly was missing. I order the pads and springs. I believe this will solve my problem. thanks for you help